/*  
 *  sha1.c  
 *  
 *  Description:  
 *      This file implements the Secure Hashing Algorithm 1 as  
 *      defined in FIPS PUB 180-1 published April 17, 1995.  
 *  
 *      The SHA-1, produces a 160-bit message digest for a given  
 *      data stream.  It should take about 2**n steps to find a  
 *      message with the same digest as a given message and  
 *      2**(n/2) to find any two messages with the same digest,  
 *      when n is the digest size in bits.  Therefore, this  
 *      algorithm can serve as a means of providing a  
 *      "fingerprint" for a message.  
 *  
 *  Portability Issues:  
 *      SHA-1 is defined in terms of 32-bit "words".  This code  
 *      uses <stdint.h> (included via "sha1.h" to define 32 and 8  
 *      bit unsigned integer types.  If your C compiler does not  
 *      support 32 bit unsigned integers, this code is not  
 *      appropriate.  
 *  
 *  Caveats:  
 *      SHA-1 is designed to work with messages less than 2^64 bits  
 *      long.  Although SHA-1 allows a message digest to be generated  
 *      for messages of any number of bits less than 2^64, this  
 *      implementation only works with messages with a length that is  
 *      a multiple of the size of an 8-bit character.  
 *  
 */   
 
#include "sha_1.h"   
   
/*  
 *  Define the SHA1 circular left shift macro  
 */   
#define SHA1CircularShift(bits,word) (((word) << (bits)) | ((word) >> (32-(bits))))   
   
/* Local Function Prototyptes */   
void SHA1PadMessage(SHA1Context *);   
void SHA1ProcessMessageBlock(SHA1Context *);   
   
/*  
 *  SHA1Reset  
 *  
 *  Description:  
 *      This function will initialize the SHA1Context in preparation  
 *      for computing a new SHA1 message digest.  
 *  
 *  Parameters:  
 *      context: [in/out]  
 *          The context to reset.  
 *  
 *  Returns:  
 *      sha Error Code.  
 *  
 */   
int SHA1Reset(SHA1Context *context)   
{   
    if (!context)   
    {   
        return shaNull;   
    }   
   
    context->Length_Low             = 0;   
    context->Length_High            = 0;   
    context->Message_Block_Index    = 0;   
   
    context->Intermediate_Hash[0]   = 0x67452301;   
    context->Intermediate_Hash[1]   = 0xEFCDAB89;   
    context->Intermediate_Hash[2]   = 0x98BADCFE;   
    context->Intermediate_Hash[3]   = 0x10325476;   
    context->Intermediate_Hash[4]   = 0xC3D2E1F0;   
   
    context->Computed   = 0;   
    context->Corrupted  = 0;   
   
    return shaSuccess;   
}   
   
/*  
 *  SHA1Result  
 *  
 *  Description:  
 *      This function will return the 160-bit message digest into the  
 *      Message_Digest array  provided by the caller.  
 *      NOTE: The first octet of hash is stored in the 0th element,  
 *            the last octet of hash in the 19th element.  
 *  
 *  Parameters:  
 *      context: [in/out]  
 *          The context to use to calculate the SHA-1 hash.  
 *      Message_Digest: [out]  
 *          Where the digest is returned.  
 *  
 *  Returns:  
 *      sha Error Code.  
 *  
 */   
int SHA1Result(SHA1Context *context, uint8_t Message_Digest[SHA1HashSize])   
{   
    int i;   
   
    if (!context || !Message_Digest)   
    {   
        return shaNull;   
    }   
   
    if (context->Corrupted)   
    {   
        return context->Corrupted;   
    }   
   
    if (!context->Computed)   
    {   
        SHA1PadMessage(context);   
        for(i=0; i<64; ++i)   
        {   
            /* message may be sensitive, clear it out */   
            context->Message_Block[i] = 0;   
        }   
        context->Length_Low = 0;    /* and clear length */   
        context->Length_High = 0;   
        context->Computed = 1;   
   
    }   
   
    for(i = 0; i < SHA1HashSize; ++i)   
    {   
        Message_Digest[i] = context->Intermediate_Hash[i>>2]   
                            >> 8 * ( 3 - ( i & 0x03 ) );   
    }   
   
    return shaSuccess;   
}   
   
/*  
 *  SHA1Input  
 *  
 *  Description:  
 *      This function accepts an array of octets as the next portion  
 *      of the message.  
 *  
 *  Parameters:  
 *      context: [in/out]  
 *          The SHA context to update  
 *      message_array: [in]  
 *          An array of characters representing the next portion of  
 *          the message.  
 *      length: [in]  
 *          The length of the message in message_array  
 *  
 *  Returns:  
 *      sha Error Code.  
 *  
 */   
int SHA1Input(SHA1Context* context, const uint8_t* message_array, unsigned length)   
{   
    if (!length)   
    {   
        return shaSuccess;   
    }   
   
    length = length;   
    length = length;   
   
    if (!context || !message_array)   
    {   
        return shaNull;   
    }   
   
    if (context->Computed)   
    {   
        context->Corrupted = shaStateError;   
   
        return shaStateError;   
    }   
   
    if (context->Corrupted)   
    {   
         return context->Corrupted;   
    }   
    while(length-- && !context->Corrupted)   
    {
      context->Message_Block[context->Message_Block_Index++] = (*message_array & 0xFF);   
   
      context->Length_Low += 8;   
      if (context->Length_Low == 0)   
      {   
        context->Length_High++;   
        if (context->Length_High == 0)   
        {   
            /* Message is too long */   
            context->Corrupted = 1;   
        }   
      }   
   
      if (context->Message_Block_Index == 64)   
      {   
        SHA1ProcessMessageBlock(context);   
      }   
   
      message_array++;   
    }   
   
    return shaSuccess;   
}   
   
/*  
 *  SHA1ProcessMessageBlock  
 *  
 *  Description:  
 *      This function will process the next 512 bits of the message  
 *      stored in the Message_Block array.  
 *  
 *  Parameters:  
 *      None.  
 *  
 *  Returns:  
 *      Nothing.  
 *  
 *  Comments:  
  
 *      Many of the variable names in this code, especially the  
 *      single character names, were used because those were the  
 *      names used in the publication.  
 *  
 *  
 */   
void SHA1ProcessMessageBlock(SHA1Context *context)   
{   
    const uint32_t K[] =    {       /* Constants defined in SHA-1   */   
                            0x5A827999,   
                            0x6ED9EBA1,   
                            0x8F1BBCDC,   
                            0xCA62C1D6   
                            };   
    int           t;                 /* Loop counter                */   
    uint32_t      temp;              /* Temporary word value        */   
    uint32_t      W[80];             /* Word sequence               */   
    uint32_t      A, B, C, D, E;     /* Word buffers                */   
   
    /*  
     *  Initialize the first 16 words in the array W  
     */   
    for(t = 0; t < 16; t++)   
    {   
        W[t] = context->Message_Block[t * 4] << 24;   
        W[t] |= context->Message_Block[t * 4 + 1] << 16;   
        W[t] |= context->Message_Block[t * 4 + 2] << 8;   
        W[t] |= context->Message_Block[t * 4 + 3];   
    }   
   
    for(t = 16; t < 80; t++)   
    {   
       W[t] = SHA1CircularShift(1,W[t-3] ^ W[t-8] ^ W[t-14] ^ W[t-16]);   
    }   
   
    A = context->Intermediate_Hash[0];   
    B = context->Intermediate_Hash[1];   
    C = context->Intermediate_Hash[2];   
    D = context->Intermediate_Hash[3];   
    E = context->Intermediate_Hash[4];   
   
    for(t = 0; t < 20; t++)   
    {   
        temp =  SHA1CircularShift(5,A) +   
                ((B & C) | ((~B) & D)) + E + W[t] + K[0];   
        E = D;   
        D = C;   
        C = SHA1CircularShift(30,B);   
   
        B = A;   
        A = temp;   
    }   
   
    for(t = 20; t < 40; t++)   
    {   
        temp = SHA1CircularShift(5,A) + (B ^ C ^ D) + E + W[t] + K[1];   
        E = D;   
        D = C;   
        C = SHA1CircularShift(30,B);   
        B = A;   
        A = temp;   
    }   
   
    for(t = 40; t < 60; t++)   
    {   
        temp = SHA1CircularShift(5,A) +   
               ((B & C) | (B & D) | (C & D)) + E + W[t] + K[2];   
        E = D;   
        D = C;   
        C = SHA1CircularShift(30,B);   
        B = A;   
        A = temp;   
    }   
   
    for(t = 60; t < 80; t++)   
    {   
        temp = SHA1CircularShift(5,A) + (B ^ C ^ D) + E + W[t] + K[3];   
        E = D;   
        D = C;   
        C = SHA1CircularShift(30,B);   
        B = A;   
        A = temp;   
    }   
   
    context->Intermediate_Hash[0] += A;   
    context->Intermediate_Hash[1] += B;   
    context->Intermediate_Hash[2] += C;   
    context->Intermediate_Hash[3] += D;   
    context->Intermediate_Hash[4] += E;   
   
    context->Message_Block_Index = 0;   
}   
   
/*  
 *  SHA1PadMessage  
 *  
  
 *  Description:  
 *      According to the standard, the message must be padded to an even  
 *      512 bits.  The first padding bit must be a '1'.  The last 64  
 *      bits represent the length of the original message.  All bits in  
 *      between should be 0.  This function will pad the message  
 *      according to those rules by filling the Message_Block array  
 *      accordingly.  It will also call the ProcessMessageBlock function  
 *      provided appropriately.  When it returns, it can be assumed that  
 *      the message digest has been computed.  
 *  
 *  Parameters:  
 *      context: [in/out]  
 *          The context to pad  
 *      ProcessMessageBlock: [in]  
 *          The appropriate SHA*ProcessMessageBlock function  
 *  Returns:  
 *      Nothing.  
 *  
 */   
   
void SHA1PadMessage(SHA1Context *context)   
{   
    /*  
     *  Check to see if the current message block is too small to hold  
     *  the initial padding bits and length.  If so, we will pad the  
     *  block, process it, and then continue padding into a second  
     *  block.  
     */   
    if (context->Message_Block_Index > 55)   
    {   
        context->Message_Block[context->Message_Block_Index++] = 0x80;   
        while(context->Message_Block_Index < 64)   
        {   
            context->Message_Block[context->Message_Block_Index++] = 0;   
        }   
   
        SHA1ProcessMessageBlock(context);   
   
        while(context->Message_Block_Index < 56)   
        {   
            context->Message_Block[context->Message_Block_Index++] = 0;   
        }   
    }   
    else   
    {   
        context->Message_Block[context->Message_Block_Index++] = 0x80;   
        while(context->Message_Block_Index < 56)   
        {   
   
            context->Message_Block[context->Message_Block_Index++] = 0;   
        }   
    }   
   
    /*  
     *  Store the message length as the last 8 octets  
     */   
    context->Message_Block[56] = context->Length_High >> 24;   
    context->Message_Block[57] = context->Length_High >> 16;   
    context->Message_Block[58] = context->Length_High >> 8;   
    context->Message_Block[59] = context->Length_High;   
    context->Message_Block[60] = context->Length_Low >> 24;   
    context->Message_Block[61] = context->Length_Low >> 16;   
    context->Message_Block[62] = context->Length_Low >> 8;   
    context->Message_Block[63] = context->Length_Low;   
   
    SHA1ProcessMessageBlock(context);   
}   